The first Constitutional Convention passed Articles of Confederation in 1781.
Martin Van Buren, born the following year 1782, was the first American president.
The presidents before him can only be the American “citizens” mentioned as eligible for either offices, the presidency or vice presidency, as set forth in Article 2, Section, 1, clause 5. All of the presidents before Van Buren were born in British American colonies. All of the presidents, including and following Van Buren were born in one of the state’s of the United States of America. They were not just citizens. They were also “natural born citizens”.
See, the problem was that if the Framers had limited eligibility for both offices to natural born citizens instead of just citizens, they would have made all Americans ineligible for the offices— until an American was born in the USA.
So where does the logic lead us?
The Framers intended the term “natural born citizen” to require birth in the United States of America, making the person a citizen as well, so that a citizen might also be a natural born citizen, and a natural born citizen was a citizen who had fulfilled another condition as well.
But the legal status of citizenship did not necessarily include natural born citizenship.
Principles of parsimony, rules of construction and plain common sense lead to no other conclusion.
You need to reread Article 2, Section, 1, clause 5 and notice the time frame.
You also need to read Article 1, Section 8, clause 4 , the first half.